针对在激光三角法测量中,像点光强分布不规则变化导致质心法测量精度下降的问题,提出基于动态模板的归一化互相关函数法(N C C)计算像点位移。该方法将线阵C C D当前帧采集的像点图像作为下一帧图像的匹配模板,利用NCC法计算前后两帧像...针对在激光三角法测量中,像点光强分布不规则变化导致质心法测量精度下降的问题,提出基于动态模板的归一化互相关函数法(N C C)计算像点位移。该方法将线阵C C D当前帧采集的像点图像作为下一帧图像的匹配模板,利用NCC法计算前后两帧像点的相对位移。以金属表面作为被测表面进行了实测,实验结果表明,动态模板的NCC法对像点光强变化具有较高的鲁棒性,测量精度为1%,绝对误差不大于6μm。该方法相对于传统质心法在测量强反射表面位移时具有较大优势,对拓宽三角测量的适用范围有一定帮助。展开更多
A ceramic ball is a basic part widely used in precision bearings.There is no perfect testing equipment for ceramic ball surface defects at present.A fast visual detection algorithm for ceramic ball surface defects bas...A ceramic ball is a basic part widely used in precision bearings.There is no perfect testing equipment for ceramic ball surface defects at present.A fast visual detection algorithm for ceramic ball surface defects based on fringe reflection is designed.By means of image preprocessing,grayscale value accumulative differential positioning,edge detection,pixel-value row difference and template matching,the algorithm can locate feature points and judge whether the spherical surface has defects by the number of points.Taking black silicon nitride ceramic balls with a diameter of 6.35 mm as an example,the defect detection time for a single gray scale image is 0.78 s,and the detection limit is 16.5μm.展开更多
In the laser displacement sensors measurement system,the laser beam direction is an important parameter.Particularly,the azimuth and pitch angles are the most important parameters to a laser beam.In this paper,based o...In the laser displacement sensors measurement system,the laser beam direction is an important parameter.Particularly,the azimuth and pitch angles are the most important parameters to a laser beam.In this paper,based on monocular vision,a laser beam direction measurement method is proposed.First,place the charge coupled device(CCD)camera above the base plane,and adjust and fix the camera position so that the optical axis is nearly perpendicular to the base plane.The monocular vision localization model is established by using circular aperture calibration board.Then the laser beam generating device is placed and maintained on the base plane at fixed position.At the same time a special target block is placed on the base plane so that the laser beam can project to the special target and form a laser spot.The CCD camera placed above the base plane can acquire the laser spot and the image of the target block clearly,so the two-dimensional(2D)image coordinate of the centroid of the laser spot can be extracted by correlation algorithm.The target is moved at an equal distance along the laser beam direction,and the spots and target images of each moving under the current position are collected by the CCD camera.By using the relevant transformation formula and combining the intrinsic parameters of the target block,the2D coordinates of the gravity center of the spot are converted to the three-dimensional(3D)coordinate in the base plane.Because of the moving of the target,the3D coordinates of the gravity center of the laser spot at different positions are obtained,and these3D coordinates are synthesized into a space straight line to represent the laser beam to be measured.In the experiment,the target parameters are measured by high-precision instruments,and the calibration parameters of the camera are calibrated by a high-precision calibration board to establish the corresponding positioning model.The measurement accuracy is mainly guaranteed by the monocular vision positioning accuracy and the gravity center extraction accuracy.The experimental results show the maximum error of the angle between laser beams reaches to0.04°and the maximum error of beam pitch angle reaches to0.02°.展开更多
Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve...Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve of a train,the speed of which is over200km/h.Nevertheless the method has two limitations,one is large field-〇f-view(FO V),the other is calibration time.Hence portable calibration equipment,easy-t〇-build target and rapid calibration algorithm are required to complete the calibration.In this paper,a new rapid on-site calibration method with large FOV based on binocular stereo vision is proposed.To address these issues,a light target has been designed,the rail coordinate system(RCS)is represented by40fixed retroreflective points on the target,and they are utilized to calibrate the parameters of two cameras.In addition,two cameras merely capture a single image of the target simultaneously,and the intrinsic and extrinsic parameters of the cameras can be calculated rapidly.To testify the proposed method,the experiments have been conducted and the results reveal that the accuracy can reach+1mm,which can meet the measurement requirement.展开更多
A single-axis normal-tracking measurement system is proposed, which can solve the problem of measuring large curved surface. According to Collins formula, the tilt dependent error of the measurement system is studied,...A single-axis normal-tracking measurement system is proposed, which can solve the problem of measuring large curved surface. According to Collins formula, the tilt dependent error of the measurement system is studied, which uses Gaussian beam as the light source. By theoretical analysis and numerical simulation, the influence of the error is presented. The results show that there is the difference between point source and Gaussian beam for differential confocal microscopy. The opti-mal diameter of pinhole can be determined by the mathematical model and the actual parameters of the measurement system. The optimal pinhole diameter of this measurement system is 20 to 35 pm for 633 nm wavelength light source.展开更多
文摘针对在激光三角法测量中,像点光强分布不规则变化导致质心法测量精度下降的问题,提出基于动态模板的归一化互相关函数法(N C C)计算像点位移。该方法将线阵C C D当前帧采集的像点图像作为下一帧图像的匹配模板,利用NCC法计算前后两帧像点的相对位移。以金属表面作为被测表面进行了实测,实验结果表明,动态模板的NCC法对像点光强变化具有较高的鲁棒性,测量精度为1%,绝对误差不大于6μm。该方法相对于传统质心法在测量强反射表面位移时具有较大优势,对拓宽三角测量的适用范围有一定帮助。
基金National Science and Technology Major Project of China(No.2016ZX04003001)。
文摘A ceramic ball is a basic part widely used in precision bearings.There is no perfect testing equipment for ceramic ball surface defects at present.A fast visual detection algorithm for ceramic ball surface defects based on fringe reflection is designed.By means of image preprocessing,grayscale value accumulative differential positioning,edge detection,pixel-value row difference and template matching,the algorithm can locate feature points and judge whether the spherical surface has defects by the number of points.Taking black silicon nitride ceramic balls with a diameter of 6.35 mm as an example,the defect detection time for a single gray scale image is 0.78 s,and the detection limit is 16.5μm.
基金National Science and Technology Major Project of China(No.2016ZX04003001)Tianjin Research Program of Application Foundation and Advanced Technology(No.14JCZDJC39700)
文摘In the laser displacement sensors measurement system,the laser beam direction is an important parameter.Particularly,the azimuth and pitch angles are the most important parameters to a laser beam.In this paper,based on monocular vision,a laser beam direction measurement method is proposed.First,place the charge coupled device(CCD)camera above the base plane,and adjust and fix the camera position so that the optical axis is nearly perpendicular to the base plane.The monocular vision localization model is established by using circular aperture calibration board.Then the laser beam generating device is placed and maintained on the base plane at fixed position.At the same time a special target block is placed on the base plane so that the laser beam can project to the special target and form a laser spot.The CCD camera placed above the base plane can acquire the laser spot and the image of the target block clearly,so the two-dimensional(2D)image coordinate of the centroid of the laser spot can be extracted by correlation algorithm.The target is moved at an equal distance along the laser beam direction,and the spots and target images of each moving under the current position are collected by the CCD camera.By using the relevant transformation formula and combining the intrinsic parameters of the target block,the2D coordinates of the gravity center of the spot are converted to the three-dimensional(3D)coordinate in the base plane.Because of the moving of the target,the3D coordinates of the gravity center of the laser spot at different positions are obtained,and these3D coordinates are synthesized into a space straight line to represent the laser beam to be measured.In the experiment,the target parameters are measured by high-precision instruments,and the calibration parameters of the camera are calibrated by a high-precision calibration board to establish the corresponding positioning model.The measurement accuracy is mainly guaranteed by the monocular vision positioning accuracy and the gravity center extraction accuracy.The experimental results show the maximum error of the angle between laser beams reaches to0.04°and the maximum error of beam pitch angle reaches to0.02°.
基金National Science and Technology Major Project of China(No.2016ZX04003001)
文摘Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve of a train,the speed of which is over200km/h.Nevertheless the method has two limitations,one is large field-〇f-view(FO V),the other is calibration time.Hence portable calibration equipment,easy-t〇-build target and rapid calibration algorithm are required to complete the calibration.In this paper,a new rapid on-site calibration method with large FOV based on binocular stereo vision is proposed.To address these issues,a light target has been designed,the rail coordinate system(RCS)is represented by40fixed retroreflective points on the target,and they are utilized to calibrate the parameters of two cameras.In addition,two cameras merely capture a single image of the target simultaneously,and the intrinsic and extrinsic parameters of the cameras can be calculated rapidly.To testify the proposed method,the experiments have been conducted and the results reveal that the accuracy can reach+1mm,which can meet the measurement requirement.
基金Quantity Dissemination and Quality Safety Project of AQSIQ(No.ALC1501)National Key Scientific Instrument and Equipment Development Projects,China(No.2013YQ170539)
文摘A single-axis normal-tracking measurement system is proposed, which can solve the problem of measuring large curved surface. According to Collins formula, the tilt dependent error of the measurement system is studied, which uses Gaussian beam as the light source. By theoretical analysis and numerical simulation, the influence of the error is presented. The results show that there is the difference between point source and Gaussian beam for differential confocal microscopy. The opti-mal diameter of pinhole can be determined by the mathematical model and the actual parameters of the measurement system. The optimal pinhole diameter of this measurement system is 20 to 35 pm for 633 nm wavelength light source.
